This application claims the priority of German Application No. 103 07 182.2 filed Feb. 20, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and a device for checking the air noise of a motor vehicle.
Air noise is generated by a passenger car in operation, specifically by the flow around an outer skin of a vehicle body, in two fashions: First, by a turbulent boundary layer when the flow is adjacent to the outer skin, and secondly, by a steady and unsteady separation and reapplication of the flow from and to the outer skin respectively. Because of the turbulent boundary layer, an alternating pressure of the flow acts upon the surface of the outer skin which generates airborne noise (sound waves propagate in the gaseous air medium) as well as structure-borne noise (sound waves propagate in a solid body).
A wind tunnel (German Patent Document DE 41 39 359 A1, corresponding U.S. Pat. No. 5,435,175) is known which is equipped with an open-jet working section and with a wind tunnel nozzle which can be swivelled for generating a flow which can be varied in its direction while the wind tunnel is running. In addition, this wind tunnel can be equipped with acoustically effective devices which are integrated in the flow guidance. This has the purpose of lowering the sound pressure level to such an extent that the flow noise, which is a function of the direction of the air flow, can also be perceived and measured.
German Patent Document DE 39 39 099 A1 relates to a checking device for frontal radiator parts of a motor vehicle through which air can flow at different rates of air flow. In this case, a funnel is disposed in front of a radiator of the motor vehicle. The cross-section of the funnel widens toward the radiator and its outlet opening extends approximately flush with a contour of a cooling-air inlet opening. In addition, the checking device comprises a controllable blower which is provided in the vicinity of the inlet opening of the funnel.
It is an object of the invention to develop a method and a device for checking the air noise of a motor vehicle, particularly of a passenger car, by which the qualitative assessment of the passenger car with respect to air noise perceivable by vehicle occupants is further optimized. The method and the device should be distinguished by simplicity and an easy implementability.
According to the invention, this object is achieved by providing a method of checking air noise of a motor vehicle, particularly of a passenger car, which is generated by air flowing onto an outer skin of a vehicle body of the passenger car, comprising applying targeted air currents to a stationary passenger car in predetermined areas of the outer skin where sealing devices extend between stationary vehicle body structures and movable vehicle body elements of the vehicle body, and measuring the air noise occurring as a result of the air currents.
This object is also achieved by providing a device for carrying out the method referred to above, wherein the targeted air currents are generated by a flow device with a blower and a blast nozzle for acting on predetermined measuring points of the vehicle.
Further features and advantages of the preferred embodiments of the invention are described herein and in the claims.
Important advantages achieved by the invention are that, while the passenger car is standing, as a result of applying targeted air currents to defined areas of the outer skin, by means of the method, the air noise can be subjectively and/or objectively determined in a simple manner. As a result, high-expenditure test drives of the passenger car on test tracks or public roads and possible checks are avoided. When, in addition, retouching is required on a motor vehicle, this can be carried out more easily in connection with the method. Currents of air are applied to the outer skin by means of a blower, in which case, defined measuring points, for example, of a door of the vehicle body, are acted upon by the blower. A flow device is suitable for this purpose which has the blower comprising an outflow cross-section and a blast nozzle used for acting upon the measuring points. Preferably, a sound absorber is connected behind the blower, and a conveying hose is provided between the blast nozzle and the sound absorber. Finally, the blower, the sound absorber, the conveying hose and the blast nozzle can be combined to form a constructional unit.
An embodiment of the invention is illustrated in the drawing and will be described in detail in the following.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.